1. Field of the Invention
This invention relates to a method for aftertreatment of one-piece high-grade steel castings, produced from circular high-grade steel blanks or cut-to-size blanks capable of being deep-drawn by deep-drawing, punching, rolling and shaping.
2. Discussion of Related Art
Tensions occur in the material, particularly when producing high-grade steel castings from circular high-grade steel blanks or cut-to-size blanks enclosing a hollow space or partial hollow space of varied sizes, which lead to breaks or cracks in the material, so that the parts produced are no longer suitable for many types of use. Thus many of the high-grade steel castings produced in this way must be considered to be waste. This applies particularly to sleeve-shaped high-grade steel castings, which are used as covers for the ends of motor vehicle exhaust pipes.
For these reasons, such covers of high-grade steel castings are not shaped in one piece from circular high-grade steel blanks or cut-to-size blanks, but are made in the customary way by bending and welding. However, this requires considerably greater production costs, because the weld seam does not only have to be finished, but it also adversely affects the appearance of the high-grade steel blank.